An example of this can be found in the `save` method of the base model class, `django.db.models.Model`; the file in which that class is defined imports the signals defined in the `django.db.models` module:

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{{{ from django.db.models import signals }}}

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{{{

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from django.db.models import signals

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}}}

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It also imports the dispatcher:

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{{{ from django.dispatch import dispatcher }}}

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{{{

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from django.dispatch import dispatcher

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}}}

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And in the very last line of the `save` method, it sends the `post_save` signal:

The `management.py` file also imports `django.db.models.signals` and `django.dispatch.dispatcher`; after the `create_contenttypes` function is defined, it sets up that function to listen for the `post_syncdb` signal:

The first argument, `create_contenttypes`, is the name of the function to execute when the signal is sent out. The second argument, `signal`, is the signal to listen for. There is another optional argument, `sender`, which is not used in this example; `sender` can be used to narrow down exactly what will be listened for; when you specify `sender`, your function will only be executed when the object which sent the signal is the same as the object you specify as the `sender` argument.

An example of this can be found in Django's authentication application: `django.contrib.auth.management` defines a function called `create_superuser`, and uses the dispatcher to connect to the `post_syncdb` signal -- but ''only'' when `post_syncdb` is being sent as a result of installing the auth application. To do this, the auth app's `management.py` file imports its own models:

* `instance` -- the instance of the model you just created. For example, in the tutorial when you do `p = Poll(question="What's up?", pub_date=datetime.now())`, the `instance` argument to the `post_init` signal would be the `Poll` object you just created.

* `interactive` -- whether `manage.py` is running in "interactive" mode; this is a boolean and so is either `True` or `False`. If `interactive` is `True`, it's safe to prompt the user to input things on the command line (for example, the auth app only prompts to create a superuser when `interactive` is `True`); if `interactive` is `False`, functions which listen for this signal should not try to prompt for anything.